Impact of puroindoline b alleles on the genetic variation for hardness in soft × hard wheat crosses

Wheat grain hardness is controlled by one major genetic factor, the puroindoline hardness (ha) locus on the short arm of chromosome 5D, but there is also evidence for other minor genetic factors modifying the effect of puroindoline alleles. In this study, the progeny of nine soft × hard wheat crosses was evaluated for kernel texture, and the allelic state of puroindoline b (pinB) was assessed by polymerase chain reaction. The F₂ populations of all nine crosses showed the expected 1:2:1 segregation ratio of homozygous soft, heterozygous medium and homozygous hard offspring. A model of variance components was constructed to separate the effects of pinB‐D1 allelic variation from other genetic factors affecting endosperm hardness. This model showed that pinB‐D1 allelic variation could explain 75‐93% of the genetic variation for hardness in the F₂, but there were also significant contributions from other genetic factors in all the crosses. The feasibility of pinB‐D1 alleles as a molecular marker for hardness is demonstrated, and the results also indicate the possibility of breeding wheat varieties with true medium hardness.